I. Technological Field
The present invention relates to a building material, a building and a method for controlling the indoor environment in a building.
II. Description of Related Art
Conventional houses for cultivating plants, such as greenhouses, have been configured to have a roof, a wall or the like formed from a transparent sheet, such as a transparent plastic sheet or a glass sheet.
Plant cultivation has tended to be done in a large scale, which has made such houses for cultivating plants larger.
Such houses for cultivating plants, in particular large-sized houses for cultivating plants, are required to improve durability, a thermal insulation property, ease in maintenance and the like.
It has been proposed to form a roof, a wall or the like from a combination of two transparent plastic films in order to build a house having an excellent thermal insulation property. For example, JP-A-2004-81205 has proposed a roof wherein two transparent plastic films are formed in a bag-like structure and are fixed to a ridgepole or the like to provide a bag-like structure, and air is supplied into the bag-like structure to stretch the bag-like structure tight. A building using such a roof can supply warm air in the bag-like structure forming the roof, easily melting snow piled on the roof and easily keeping the indoor area warm.
In houses for cultivating plants, it has been prevalent that a shade curtain is put therein to block excessive light from entering from outside mainly in the summer. With regard to such a shade curtain, various proposals have been made (see JP-A-9-234829).
However, such a shade curtain needs to dispose a device for opening and closing the curtain in the house. Such a shade curtain, which constantly exists in the house, produces a shade, which make the amount of light nonuniform between a shaded portion and an unshaded portion, with the result that the qualities or the growing levels of cultivated plants are made different in some cases. Such a shade curtain and the device opening and closing the curtain require maintenance. For these reasons, it has been demanded to develop a light-blocking system, which has a simpler structure and makes it difficult to make the amount of light nonuniform indoors.
Further, such houses for cultivating plants have been demanded to realize indoor environments (such as an amount of light, a temperature and a humidity) suited for plants under such circumstances that cultivated plants are diversified and that the qualities sought for plants (such as the colors and the tastes of vegetables or flowers) are diversified. In particular, the control of the amount of light is important since the amount of light has a great impact on plants. However, the above-mentioned shade curtain is difficult to finely control the amount of light since only two-stage control of blocking or unblocking light can be made.